(1) Field of the Invention
The invention relates to a method and apparatus for pre-hatch avian embryo sex determination. In particular, the invention relates to a non-invasive method and apparatus for determining the sex of avian species while in the egg and sorting the eggs into groups consisting primarily of either male or female embryos, and other groups consisting of eggs that are unusable. The invention uses a non-invasive imaging method, such as nuclear magnetic resonance, to make the sex determination.
(2) Description of the Related Art
Sex separate rearing is an important component for much of the broiler and essentially all egg layer and turkey production. Essentially all commercial hatcheries of pullets that will become table egg laying hens and commercial turkey hatcheries use sex separate rearing of flocks, and approximately 15-30% of the commercial hatcheries producing broilers use sex separate rearing of flocks. Depending on hatchery output and production and processing/marketing requirements, and cost relationships sex separate rearing can be of economic benefit to poultry producers.
Currently, there are three methods available for sexing poultry. Day-old chicks can be sexed either by vent sexing, or feather sexing methods. Alternatively, male and female chicks can be reared together until secondary sex characteristics become apparent, then the chicks can be separated based on sex and reared separately.
Vent sexing relies on the visual identification of sex based on the appearance of sex related anatomical structures. Vent sexing of chicks at hatching has complications that make it more difficult than sex determination of other animals. The reason is that the sex organs of birds are located within the body and are not easily distinguishable. For example, while the vent specific copulatory structures of aves can be identified by shape, there are over fifteen different shapes to consider. Therefore, vent sexing requires highly trained individuals who have undergone a difficult and lengthy training period which makes the method expensive.
Feather sexing is based on feather characteristics that differ between male and female chicks. The two commercial uses of feather sexing are down color pattern, and rapid/slow rate of growth of the wing feathers, with the rapid feathering gene being used extensively. The method is relatively easy to learn, however feather appearances are determined by specially selected genetic traits that must be present in the chick strain. Most strains (breeds) of chickens have these feather sexing characteristics but turkeys and other aves may not, so feathering of both sexes appear identical. Therefore, feather sexing is not available for sexing in many poultry operations.
The third method of sexing chickens relies on the appearance of natural secondary sex characteristics. In males, the combs and wattles will become larger than those on females and the head will become more angular and masculine looking. The female will remain smaller than the male and is more refined in appearance. In some breeds, the feathers of each sex will develop a characteristic color pattern which facilitates sexing. Sexing based on secondary sex characteristics can usually be performed after the chicks reach four to six weeks of age.
The disadvantages of vent sexing include the difficulty in identifying the sex of a bird and the need for highly skilled personnel to make the individual vent sexing decisions which makes the method expensive. While easier to perform, feather sexing has the disadvantage of being limited to specific genetic crosses of birds. However, maintenance of genetic capacity to allow feather sexing places added constraints on breeding programs that could be reduced if a non-invasive procedure of sex determination was used. Sexing by secondary sex characteristics is the easiest method to perform but has the disadvantage of requiring birds of both sexes to be reared together for the first four to six weeks after hatch which because of feed costs and feed conversion considerations can be more expensive to the hatchery than the expense of vent sexing.
In the United States it presently costs approximately $10 million dollars a year to sex 230 million chicks destined for table egg layer operations at a cost of $0.04 to $0.05 per female chick. At a reasonable estimate of 20% of broilers also being reared sex separate, and with most chicks being feather sexed, and a cost of $0.0075 per feather sexed chick, the cost to the broiler industry is about $9 million. Vent sexing costs are much greater than feather sexing costs because of the need for highly skilled personnel. The turkey industry utilizes vent sexing for the more than 300 million poults produced annually, which represents a cost to the industry of about $12 million. Therefore, the total cost of bird sexing to the United States poultry industry probably exceeds $30 million dollars a year.
Clearly, the commercial hatchery industry has a need for a method that would allow birds to be sorted by sex that did not rely on highly skilled individuals or on using specific genetic of crosses birds.